1. Field of the Invention
The present invention relates to a joint structure capable of reinforcing bridges and buildings, and more particularly to the joint structure with at least one restraining member capable of enhancing the buckling strength of steel plates, and the joint structure is installed on a side of a gusset plate (or a joint plate) of a truss or a diagonal brace to prevent buckling caused by lateral deformations of the gusset plate.
2. Description of Related Art
Gusset plate (also known as joint plate) is generally installed between a chord member, a beam member and a column member and connected to a truss web member or a two-force member to transmit loads, and thus the gusset plate can be applied in bridges and buildings. In general, most gusset plates are made of steel plates, and the steel plates are galvanized or coated to protect the gusset plate from being rusted, so that most galvanized steel plates can be used outdoors. Occasionally, the gusset plate is made of copper or aluminum, but the copper or aluminum gusset plate can be used only in small structures that do not require large supporting strengths. Due to the properties of copper or aluminum, the copper or aluminum gusset plates are usually used in structures outdoors.
With reference to FIG. 1A for a schematic view of a conventional gusset plate applied in a connection of braced frames, the gusset plate A2 is connected to a column structure A3 and a beam structure A4, and a diagonal brace A1 is connected to the gusset plate A2 to form a part of the conventional braced structure. The gusset plate A2 is disposed at a position where the column structure A3, the beam structure A4 and the diagonal brace A1 are connected for providing a function of transmitting forces. In general, the larger the force, the bigger is the gusset plate A2. The conventional structure can be used in bridges, and deformations and vibrations may be induced by the weight of a bridge, a car or an earthquake, such that each member will produce internal forces. In FIG. 1B, when the diagonal brace A1 bears a compression F, the diagonal brace A1 is in equilibrium with adjacent elements through the gusset plate A2. Now, the gusset plate A2 distributes the stress according to the load and stiffness. With the effect of complex geometric shape, the distribution of the stress is complicated. In addition, the conventional structure can be applied in braced frame buildings. When an earthquake occurs, the buildings will induce a lateral load caused by ground motion. Now, the diagonal brace is located on a path that transmits seismic forces most directly, and thus the diagonal brace becomes the key component for seismic resistant design, wherein the gusset plate A2 is the main component for transmitting a load into and out from the diagonal brace.
From the description above, we clearly understand the components and structure of the conventional diagonal brace structure and the gusset plate A2 capable of transmitting stress between the conventional diagonal brace members. However, when the gusset plate A2 bears a larger compression, lateral deformation and buckling will occur to affect the axial stiffness and strength of the gusset. With reference to FIG. 1B for a schematic view, showing the buckling occurred in a gusset plate when stress is induced from a conventional truss member, when the conventional diagonal brace member produces a stress, the gusset plate A2 may be subjected to a compression F, such that the gusset plate A2 is deformed to buckle, and the strength and stiffness of the gusset plate A2 will drops as the lateral deformation increases to result in asymmetrical tensile and compressive behavior of the gusset plate A2, so as to affect the seismic resistant capacity of the bridges or buildings.
At present, researchers tend to break through the conventional technologies to prevent the gusset plate from buckling too early, so that an auxiliary structure of the stiffened plate is developed. With reference to FIG. 1C for a schematic view of a conventional stiffened plate installed at an edge of a gusset plate, two conventional stiffened plates A5 are welded to two edges of the gusset plate A2 respectively to enhance the strength of the gusset plate A2. However, test results show that although the stiffened plates A5 can prevent free edges of the gusset plate A2 from occurring local buckling, yet the overall lateral deformation and buckling still may occur, and the conventional stiffened plate A5 is welded to the gusset plate A2, so that the stiffened plate will participate the axial load distribution and affect the deformation capacity of the gusset plate.
In view of the aforementioned drawbacks of the conventional gusset plate applied to a diagonal brace, the inventor of the present invention based on years of practice experience in the related industry to conduct extensive researches and experiments, and finally developed a laterally restrained joint structure in accordance with the present invention to overcome the drawbacks of the prior art.